Efforts to control insect pests have focused on methods of repelling and killing insects. Concerns are that any repellent compound be non-toxic to users, and preferably that it not be foul smelling, discoloring or staining. Additionally, concerns are that the method not be harmful to the environment or to non-target animals.
People respond to the bites and stings of arthropod pests in highly individual ways. For example, mosquitoes, fleas, and bedbugs trigger variable reactions. E. K. Markell and M. Voge, In: Medical Parasitology, 1981. Some people have only minor irritation, while others suffer painful allergic reactions that may be localized or systemic. Furthermore, previous contacts with a particular insect species may cause hypersensitive reactions in subsequent episodes.
The bites and stings of various arthropods are cause for concern not only because they are painful in and of themselves, but also because they are a means of transmission of diseases. For example, mosquitoes transmit malaria and ticks transmit lyme disease. There remains a need to protect against the bites and stings of aggressive insect pests.
In the southern United States, fire ants are an aggressive pest that annually cost some states hundreds of thousands of dollars for control efforts. The bite and sting of the fire ant is extremely painful. The burning sensation can last for up to 24 hours and following that, pustules can form, taking up to ten days to heal. Additional problems may occur if the sting becomes infected. For individuals who are particularly sensitive to the venom, a single sting can cause shock and respiratory failure.
Fire ants also attack livestock. Small animals, such as birds and mammals, have been killed by fire ant stings. Further, the ants can cause crop damage by feeding on young plants. In Florida, fire ants attack young citrus trees, causing serious economic damage.
Fire ants cause further problems because of the huge mounds they build in the soil. The mounds may reach a height of two feet and a diameter of two to three feet. These large mounds contain up to 200,000 ants. Mounds in the field may be of such large size as to become obstacles for and cause damage to mowers and farm machinery. The ants infest fields, pastures and lawns.
Attempts to control fire ants may involve drenching the mounds with pesticides. However, this method introduces toxic chemicals into the environment and often results in overapplication of the pesticide. Furthermore, eradication of individual mounds is not completely effective since smaller colonies of ants may be hidden by foliage and serve as a source for reinfestation.
Various chemical formulations have been devised to control these pests. U.S. Pat. No. 3,220,921 issued Nov. 30, 1965 to Greenbaum and Weil discloses the dimer of hexachlorocyclopentadiene, also known as Mirex. Mirex shows pronounced toxicity to fire ants when ingested, although it has low insecticidal activity with mere contact. However, Mirex has been banned in the U.S. because evidence points to its being a potent carcinogen. See The Merck Index, 11th Edition, 1989, p. 977.
Use of baits is an alternative method of controlling fire ants. When toxic pesticides are mixed with bait, the worker ants carry the bait back to the colony as food. Amdro is one such bait product that contains a slow acting poison. Although the colony will eventually be destroyed, baits are slow working; they may take up to a month to be effective. Amdro is not for use on food crops.
Chemical repellents that have low toxicity for humans may be applied to the body. Mosquito repellents that are topically applied are common. Many of the useful insect repellents are tertiary amides. Among these, an all purpose insect repellent is N,N-diethyl-m-toluamide, also known as "DEET." Notwithstanding its low toxicity, it is an irritant to eyes and mucous membranes, and ingestion can cause CNS disturbances. See The Merck Index, 11th Edition, 1989, p. 449.
What is needed are compositions that repel and kill insect pests or can be applied to the locus where insect pests are found. Such compositions need to be safe for plants and animals that come into contact with the compositions. There is a further need for compositions that prevent insects from biting and stinging. The compositions need to be non-carcinogenic, non-irritating, and non-toxic to users.